The physical layer is the lowest layer in the OSI model and deals with the mechanical and electrical specifications of connecting devices. It focuses on transmitting raw bits of data across a physical medium such as cable or wireless signals. A transmitter encodes a message into an analog or digital signal that is carried by the communications channel to a receiver. The physical layer is responsible for moving electromagnetic signals that represent a stream of binary digits from one device to another.

1. PHYSICAL LAYER
By B.Sakthi MC.A., M.Phil.,
Assistant Professor in Dept. of MCA

2. Introduction
 How to connect two or more device?
 OSI Model
 ..> Open Systems Interconnect
 Set of protocols
 Introduced in first time in 1770s by ISO
 (International Standards Organization)
 Composed of 7 Layers

3. OSI MODEL LAYERS
7. APPLICATION LAYER
6. PRESENTATIOON LAYER
5. SESSION LAYER
4. TRANSPORT LAYER
3. NETWORK LAYER
2. DATA LINK LAYER
1. PHYSICAL LAYER

4. PHYSICAL LAYER
• It deals with the mechanical and electrical specifications (Device)
• Physical characteristics of interfaces and medium.
• To move data in the form of electromagnetic signals across a transmission
medium
• The physical layer data consists of a stream of bits (sequence of 0s or 1s)
• Bits are encoded into signals

6. Signals
 A signal is an electric current or electromagnetic field used to convey data
from one place to another.
 A Transmitter encodes a message into a signal, which is carried to a receiver
by the communications channel.
 Signals Can be interpreted as either Analog or Digital